Continual tunneling of a long-distance tunnel will require replacement of damaged bits on a cutter device with tunneling being halted halfway. In order to comply with such requirement, there has been proposed a shield tunneling machine with a turnable body. This turnable body, which is disposed in a skin plate and ahead of a shield frame, is turnable about an axis perpendicular to an axis of the tunneling machine and accommodates an excavating drive with a cutter device ahead thereof, so that turning of the turnable body causes the cutter device to be directed backward, which facilitates replacement of damaged bits on the cutter device backward with tunneling being halted halfway; in this respect, words such as “forward”, “backward”, “front” and “rear” in the specification are referred to in relation with a direction of tunneling unless otherwise specified. Thus, tunneling for a long distance can be attained with damaged bits being replaced halfway of tunneling.
FIGS. 1 through 3 show a conventional shield tunneling machine comprising a shield body 1 with front and rear skin plates 7 and 2. The rear skin plate 2 has a front end within which a shield frame 3 is integrally arranged. The shield frame 3 has a number of shield jacks 4 which are arranged along an inner periphery of the rear skin plate 2 and which can be expanded to advance the shield body 1, using reaction force from segments S. Mounted on the shield frame 3 is means 5 for erecting the segments S.
The front skin plate 7, which is divertible by actuation of some of circumferentially arranged jacks 6 to change the direction of tunneling, is fitted to the rear skin plate 2 such that the former may be bent relative to the latter at their connection upon such change of the direction of tunneling.
In the front skin plate 7, there is provided a turnable shield device 8 with a turnable body 9 in the shape of for example sphere and having a turning trajectory R in the front skin plate 7. In the turnable body 9, there is provided a cylindrical wall 11 which extends longitudinally of the shield body 1 with its axis passing through a center of the turnable body 9 and which has a front annular end opened at 10 to thereby provide a cylindrical space 12. The turnable body 9 is turnably fitted via bearings 14 over shafts 13 which in turn are attached to the inner periphery of the skin plate (above and below in FIG. 1) and which have a common axis passing through the center of the turnable body 9 and perpendicular to the axis of the cylindrical wall 11 or of the shield body 1.
As shown in FIG. 3, the turnable body 9 has a plurality of pins 15 which are fixed to an outer periphery of the turnable body 9 circumferentially and equidistantly around each of the shafts 13. For each of the shafts 13, two jacks 16 extend substantially in parallel with each other and oppositely with respect to the shaft 13 as shown in FIG. 3 and are pivotally connected at their ends away from their rods to the inner periphery of the front skin plate 7. Each of rods of the jacks 16 has a catching part 17 engageable with the pin 15. Repeated expansion and contraction of one of the jacks 16 causes the pins 15 to be sequentially pushed by the catching part 17 of the one jack 16 with a result that the turnable body 9 is turned about the shaft 13 as shown by a curved arrow in FIG. 3 by, say, 180°. Repeat d expansion and contraction of the other jack 16 causes the pins 15 to be sequentially pushed by the catching part 17 of the other jack 16 with a result that the turnable body 9 is turned about the shaft 13 in a direction reverse to the above by, say, 180°. As shown in FIG. 1, the front skin plate 7 has a rear end to which a bulkhead 18 with a work port 19 is secured to enclose the turnable body 9 at its back along the turning trajectory R.
In the cylindrical wall 11, there is provided an excavating drive 22 which has a covering or cylinder 21 and is shielded at its front surface by a rotor 20 rotating around the axis of the wall 11 and a face plate 20a surrounding the rotor 20.
Arranged ahead of the rotor 20 is a cutter device 24 which is connected to the excavating drive 22 in a spaced-apart relationship via connecting members 23a. The cutter device 24 is rotatively driven via a drive center shaft 23 by a rotary drive motor 25 fixed at the axis of the cylindrical wall 11. The cutter device 24, together with the excavating drive 22 and the skin plate 7, defines a cutter chamber 24a. The rotor 20 has a man lock 26 which allows an operator to access the cutter chamber 24a. The face plate 20a is provided with slurry delivery and discharge pipes 27 and 28.
The excavating drive 22 is connected to a rear of the turnable body 9 by sliding jacks 29 such that the excavating drive 22 is movable axially of and along the cylindrical wall 11 by expansion and contraction of the sliding jacks 29. Reference numeral 30 denotes a spacer arranged between the turnable body 9 and the cylinder 21.
The front skin plate 7 has a front end with an inner circular seal 31 which contacts a spherical portion 9a of the turnable body 9 adjacent to the opening 10 to prevent soil and ground water from intruding backward.
As shown in FIGS. 1 and 2, the cutter device 24 has a plurality of (six in FIG. 2) short, radially extending, inner cutter spokes 32 each of which is fixed to the drive center shaft 23 and has a telescopic cutter spoke 34 which in turn can be radially expanded and contracted by an expansion jack 33 accommodated in the inner cutter spoke 32, a tip end of the telescopic cutter spoke 34 being substantially aligned with an outer diameter of the skin plate 7 when the telescopic cutter spoke 34 is expanded maximum. The cutter spokes 32 and 34 have a number of fixed bits 35. Each of the telescopic cutter spokes 34 has a tip end with a copy cutter 37 which is projectable and retrojectable by an expansion jack 36.
The cutter spokes 32 and 34 of the cutter device 24 are shown in FIGS. 1 and 2 to have the fixed bits 35; however, they may be provided with any kinds of bits such as roller bits.
FIG. 1 shows a state of being tunneled with the axis of the shield body 1 being aligned with that of the excavating drive 22, the cutter device 24 being increased in size or diameter through expansion of the expansion jacks 33 and thus of the telescopic cutter spokes 34.
Replacement of damaged bits 35 on the cutter device 24 will be described, starting from such state of being tunneled.
First, tunneling is halted. Then, required are reduction in diameter or contraction of the cutter device 24 into a size accommodable in the turning trajectory R and subsequent turning of the turnable body 9 to direct the cutter device 24 backward. These are carried out as follows.
In the state shown in FIGS. 1 and 2 and with tunneling being halted, the expansion jacks 33 are contracted to retract the telescopic cutter spokes 34 into the inner cutter spokes 32 and then the expansion jacks 36 are contracted to retract the copy cutters 37, thereby reducing the outer diameter of or contracting the cutter device 24. However, as may be readily seen from FIG. 1, even with the cutter device 24 being contracted, the inner cutter spokes 32 still protrude outside the turning trajectory R.
On this account, then, the spacer 30 is removed to release the engagement between the turnable body 9 and the cylinder 21 of the excavating drive 22. Then, the slurry delivery and discharge pipes 27 and 28 and the like are removed and the sliding jacks 29 are contracted to move the excavating drive 22 backward along the cylindrical wall 11 with a result that all of the cutter device 24 and the excavating drive 22 are within the turning trajectory R.
Then, the jacks 16 shown above and blow in FIG. 1 are repeatedly expanded and contracted to turn the turnable body 9 around the shafts 13 by 180° to direct the excavating drive 22 and the cutter device 24 backward. During such turning of the turnable body 9, contact between the spherical portion 9a and the seal 31 is once released, resulting in intrusion of ground water into backward of the turnable body 9; however, completion of the turning by 180° will bring about re-contact and re-sealing between the spherical portion 9a and the seal 31.
The ground water intruding into between the turnable body 9 and the bulkhead 18 is discharged through the work port 19 to dry the rear of the excavating drive 22: then, an operator enters forward of the bulkhead 18 through the work port 19 and replaces the damaged bits 35 on the cutter device 24 in a dry environment. In this chance, for example, repair of the cutter spokes 32 and 34 may be effected.
After the replacement of the damaged bits 35 on the cutter device 24, the turnable body 9 is turned about in a manner reverse to the above to re-direct the cutter device 24 forward; then, the sliding jacks 29 are expanded to advance the excavating drive 22 into a position where the front end of the front skin plate 7 may not be interfered with the telescopic cutter spokes 34 when the latter are expanded. Then, the telescopic cutter spokes 34 are expanded to increase in diameter or expand the cutter device 24. Then, tunneling is re-started.
As mentioned above, the turning of the turnable body 9 with the excavating drive 22 accommodated therein about the axis perpendicular to the axis of the skin plate 7 or of the shield body 1 so as to replace the damaged bits 35 on the cutter device 24 backward or backstage will assure safe and efficient replacement of the damaged bits 35 in a dry environment.
However, as mentioned above, the turning of the turnable body 9 about the axis perpendicular to the axis of the skin plate to direct the cutter device 24 backward requires reducing in diameter or contracting the cutter device 24 to a size accommodable in the turning trajectory R of the turnable body 9. On this account, the cutter device 24 in the conventional rotary shield device 8 has a requisite of having cutter spokes such as the cutter spokes 32 and 34.
This greatly restricts grounds which may be tunneled by a conventional shield tunneling machine with a rotary shield device.
More specifically, for the grounds with their faces readily collapsible by a slurry-shielding tunneling machine, tunneling must be effected by a shield tunneling machine having a face plate type cutter device with the faces of the grounds being held by the face plate. For tunneling of conglomerate layers, size of pebbles to be taken in must be controlled by take-in slots on a face plate. Also for tunneling of bedrock, a face plate with take-in slots is needed to control sizes of masses of rocks to be taken in. Thus, a cutter device with a face plate is often required depending upon conditions of grounds to be tunneled.
However, as mentioned above, the rotary shield device 8 which enables the damaged bits 35 to be replaced backward requires to have the cutter device 24 contractible into a size accommodable in the turning trajectory R of the turnable body 9. Conventionally, a face plate type cutter device cannot be reduced in diameter or contracted in size and therefore only the spoke type cutter device as mentioned above can be employed.
Thus, a conventional shield tunneling machine with a rotary shield device has a drawback that, for grounds which require tunneling with a face plate type cutter device, it cannot effect long-distance tunneling with damaged bits on a cutter device being replaced halfway of tunneling.